Little background. I am currently developing First person game like project. For that I am making 3d Architecture on the software 3ds max. The project has over 25 rooms which will be present on one scene. Currently I have developed 5 rooms which are over 700000 polygons.The issue which I am facing that the 3ds Max is keep crashing due to huge number of polygon. Now how can make all the rooms on one scene in 3ds max. Any suggestions?

Reduce your poly count. Use better textures.

How much memory does your PC have, and are you running a 64-bit version of 3DS Max? That seems a remarkably low polycount for the software to be crashing.

Although, as frob suggests, you are going to have trouble displaying all those polys in a game. You'll likely need to decimate the mesh and bake all the detail into normal maps.